The proposed project is an investigation of genetic restriction at the level of transcription during animal development. The system to be studied is post-gastrula development of the brine shrimp, Artemia salina. The objectives will be to try to correlate changes in the transcription apparatus with the decline in RNA synthesis that occurs during this stage of development. Soluble RNA polymerases will be purified by a combination of column chromatography, sucrose gradient centrifugation and isoelectric focusing. The subunit structure of purified polymerases will be studied by SDS gel electrophoresis and by electrofucusing. Distribution of multiple forms of RNA polymerase will be determined by column chromatography. Nuclei will be isolated from developing embryos and used to study RNA synthesis in vitro. Synthesis of pre-ribosomal RNA will be used as a criterion of fidelity of transcription. Experiments will be conducted to determine whether the decline in RNA synthesis observed in intact animals is reproduced in isolated nuclei. BIBLIOGRAPHIC REFERENCES: Birndorf, H.C., J. D'Alessio and J.C. Bagshaw. DNA-dependent RNA polymerases from Artemia embryos. Characterization of polymerases I and II from nauplius larvae. Devel. Biol. 45,34-43 (1975). Bagshaw, J.C., H.C. Birndorf and J. D'Alessio. RNA polymerases from developing Artermia embryos. Fed. Proc. 34, 685 (1975).